Carrierless ultra wideband wireless signals for conveying data

ABSTRACT

A method for conveying application data via carrierless ultra wideband wireless signals, and signals embodied in a carrierless ultra wideband waveform. Application data is encoded into wavelets that are transmitted as a carrierless ultra wideband waveform. The carrierless ultra wideband waveform is received by an antenna, and the application data is decoded from the wavelets included in the waveform. The waveforms of the signals include wavelets that have a predetermined shape that is used to modulate the data. The signals may convey, for example, Web pages and executable programs between mobile devices. The signals are low power and can penetrate obstructions making them favorable for use with a wireless node of a network.

CROSS-REFERENCE TO RELATED PATENT DOCUMENTS

[0001] This application is a continuation of U.S. application Ser. No.09/685,201, for “CARRIERLESS ULTRA WIDEBAND WIRELESS SIGNALS FORCONVEYING APPLICATION DATA,” filed Oct. 10, 2000, and is acontinuation-in-part of U.S. application Ser. No. 09/209,460, for “ULTRAWIDE BANDWIDTH SPREAD-SPECTRUM COMMUNICATIONS SYSTEM,” filed Dec. 11,1998, the contents of both of which are incorporated by reference intheir entirety.

[0002] The present document contains subject matter related to thatdisclosed in commonly owned, co-pending application Serial No.09/209,460 filed Dec. 11, 1998, entitled ULTRA WIDE BANDWIDTHSPREAD-SPECTRUM COMMUNICATIONS SYSTEM; U.S. Ser. No. 09/633,815 filedAug. 7, 2000 entitled ELECTRICALLY SMALL PLANAR UWB ANTENNA; applicationSer. No. 09/563,292, filed May 3, 2000 entitled PLANAR ULTRA WIDE BANDANTENNA WITH INTEGRATED ELECTRONICS; application Ser. No. 60/207,225filed May 26, 2000, entitled ULTRAWIDEBAND COMMUNICATIONS SYSTEM ANDMETHOD; application Ser. No. 09/685,198 filed Oct. 10, 2000, entitledANALOG SIGNAL SEPARATOR FOR UWB VERSUS NARROWBAND SIGNALS; applicationSer. No. 60/238,466 filed Oct. 10, 2000, entitled ULTRA WIDE BANDWIDTHNOISE CANCELLATION MECHANISM AND METHOD; application Ser. No. 60/217,099filed Jul. 10, 2000 entitled MULTIMEDIA WIRELESS PERSONAL AREA SYSTEMNETWORK (WPAN) PHYSICAL LAYER SYSTEM AND METHOD; application Ser. No.09/685,203 filed Oct. 10, 2000, entitled SYSTEM AND METHOD FOR BASEBANDREMOVAL OF NARROWBAND INTERFERENCE IN ULTRAWIDEBAND SIGNALS; applicationSer. No. 09/685,197 filed Oct. 10, 2000, entitled MODE CONTROLLER FORSIGNAL ACQUISITION AND TRACKING IN AN ULTRA WIDEBAND COMMUNICATIONSYSTEM; application Ser. No. 09/684,400 filed Oct. 10, 2000, entitledULTRA WIDEBAND COMMUNICATION SYSTEM, METHOD, AND DEVICE WITH LOW NOISEPULSE FORMATION; application Ser. No. 09/685,195 entitled ULTRA WIDEBANDWIDTH SYSTEM AND METHOD FOR FAST SYNCHRONIZATION; application Ser.No. 09/684,401 filed Oct. 10, 2000, entitled ULTRA WIDE BANDWIDTH SYSTEMAND METHOD FOR FAST SYNCHRONIZATION USING SUB CODE SPINS; applicationSer. No 09/685,196 filed Oct. 10, 2000, entitled ULTRA WIDE BANDWIDTHSYSTEM AND METHOD FOR FAST SYNCHRONIZATION USING MULTIPLE DETECTIONARMS; application Ser. No. 09/685,199 filed Oct. 10, 2000, entitled ALOW POWER, HIGH RESOLUTION TIMING GENERATOR FOR ULTRA-WIDE BANDWIDTHCOMMUNICATIONS SYSTEMS; application Ser. No. 09/685,202 filed Oct. 10,2000, entitled METHOD AND SYSTEM FOR ENABLING DEVICE FUNCTIONS BASED ONDISTANCE INFORMATION; application Ser. No., 09/685,201 filed Oct. 10,2000, entitled CARRIERLESS ULTRA WIDEBAND WIRELESS SIGNALS FOR CONVEYINGAPPLICATION DATA; application Ser. No., 09/685,205 filed Oct. 10, 2000,entitled SYSTEM AND METHOD FOR GENERATING ULTRA WIDEBAND PULSES;application Ser. No., 09/684,782 filed Oct. 10, 2000, entitled ULTRAWIDEBAND COMMUNICATION SYSTEM, METHOD, AND DEVICE WITH LOW NOISERECEPTION; and application Ser. No., 09/685,200 filed Oct. 10, 2000,entitled LEACKAGE NULLING RECEIVER CORRELATOR STRUCTURE AND METHOD FORULTRA WIDE BANDWIDTH COMMUNICATION SYSTEM, the entire contents of eachof which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention is directed to methods and signals forultra wideband communications, and more particularly to methods andsignals for conveying application data via carrierless ultra widebandwireless signals.

[0005] 2. Discussion of the Background

[0006] Digital information typically takes the form of a stream ofbinary pulses of a square wave, each pulse representing a bit (i.e., 1or 0) of data. To transmit a digital stream of data, it is well known touse the digital data stream to modulate a carrier waveform and totransmit the modulated carrier waveform rather than the digitalwaveform. By using modulation, a carrier waveform can be used that ismost compatible with the transmission channel. Typically, thesewaveforms are high-frequency sinusoids for transmitting signals throughspace.

[0007] A discussion of the reasons data signals are modulated ontocarriers is included in Sklar, B., “Digital Communications: Fundamentalsand Applications,” Prentice Hall, 1988, p. 118, the entire contents ofwhich are incorporated herein by reference. Signals are launched intospace via antennas. The design of an antenna is dependent on thewavelength, λ, of the signal being transmitted. A practical exampleillustrates one reason why signals are modulated onto high-frequencycarrier waves. The wavelength, λ, of a signal is equal to c/f, where cis the speed of light, or 3×10⁸ m/s, and f is the frequency of thefrequency of the signal being transmitted in Hz. It is well known bythose of ordinary skill in the digital communication art that theaperture of an antenna should be at least as large as the wavelengthbeing transmitted (see Sklar, at p. 118). Given this design constraint,it can be shown that a signal with a frequency, f, of 3000 Hz has awavelength, λ, of c/f, or 10⁵ m, which is approximately 60 miles. Ofcourse, it is not realistic to build an antenna with a 60 mile aperture.However, if that same signal is modulated onto a 30 GHz carrier prior totransmitting it, the antenna can have an aperture of less than ½ inch(see Sklar, at p. 118).

[0008] Another consideration is the bandwidth required to transmit anideal square wave. An unmodulated, unshaped ideal square wave requiresan infinite amount of bandwidth in the frequency domain. For thisreason, it is well known to shape the digital pulses using a filter thatwill round the edges of the square wave, thereby narrowing the bandwidthof the transmitted signal. Pulse shaping and modulation are discussed inWebb, W., “The Complete Wireless Communications Professional: A Guidefor Engineers and Managers,” Artech House Publishers, 1999, pp. 55-64,the entire contents of which is incorporated herein by reference.

[0009] When digital information is modulated onto a carrier andtransmitted through space, the power spectral density of that signaltends to be concentrated about the frequency of the carrier itself.These signals are normally generated with large antennas and at highpower so that the signal is not interfered with by noise. The frequencyspectrum is, of course, regulated in the United States by the FederalCommunications Commission (FCC). Regulation of the frequency spectrumensures that there will not be interference within the various allocatedfrequency ranges. Since all frequency bands contain noise, there is nopractical reason to regulate transmissions that are lower than thenoise.

[0010] With the popularization of the Internet, laptop personalcomputers, personal digital assistants (PDAs), and cellular telephones,society has become more and more dependent on the availability ofinformation and the ability to share information. With theminiaturization of computing power, many users of information are nowdemanding mobile access to their information. Using conventionalmethods, exchanging, and sharing information requires access to networkvia a telephone connection, or through a direct connection to thenetwork itself. The need for a network limits access to and sharing ofinformation to those that can access the network.

[0011] The challenge, then, as presently recognized, is to develop anapproach for transmitting and receiving information using, for example,mobile devices such as PDAs, cellular telephones, and laptop personalcomputers. It would be advantageous if the approach was wireless,eliminating the need for direct connection between the sharing devices.It would be advantageous if the approach were to employ communicationstechniques that would not fall under the jurisdiction of regulatoryagencies, thereby allowing for global use.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide a method forcommunicating information using carrierless wireless signals.

[0013] The inventors of the present invention have recognized that lowpower carrierless transmissions can be effectively used to communicateat high data rates without interfering with narrowband or spreadspectrum signals, and if the power is kept sufficiently low, thetransmissions do not need to be as broadcast devices. Accordingly,another object of the present invention is to encode digital data intomulti-phase wavelets that can be transmitted without a carrier at lowpower and at high data rates over short distances.

[0014] In one embodiment, the present invention is implemented as amethod for conveying application data with carrierless ultra widebandwireless signals. The application data is encoded into wavelets that aretransmitted without modulating them onto a carrier waveform. In anotherembodiment, the present invention is implemented as a computer datasignal that is embodied in a carrierless ultra wideband waveform.

[0015] Consistent with the title of this section, the above summary isnot intended to be an exhaustive discussion of all the features orembodiments of the present invention. A more complete, although notnecessarily exhaustive, description of the features and embodiments ofthe invention is found in the section entitled “DESCRIPTION OF THEPREFERRED EMBODIMENTS.”

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A more complete appreciation of the present invention, and manyof the attendant advantages thereof, will be readily obtained as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

[0017]FIG. 1a is a block diagram of an ultra-wide band (UWB)transceiver, according to the present invention;

[0018]FIG. 1b is a diagram for illustrating the operation of thetransceiver of FIG. 1a, according to the present invention;

[0019]FIG. 2 is a block diagram of the transceiver of FIG. 1a, thatmanipulates a shape of UWB pulses, according to the present invention;and

[0020]FIG. 3 is a schematic illustration of a general-purposemicroprocessor-based or digital signal processor-based system, which canbe programmed according to the teachings of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021]FIG. 1a is a block diagram of an ultra-wide band (UWB)transceiver. In FIG. 1a, the transceiver includes three majorcomponents, namely, receiver 11, radio controller and interface 9, andtransmitter 13. Alternatively, the system may be implemented as aseparate receiver 11 and radio controller and interface 9, and aseparate transmitter 13 and radio controller and interface 9. The radiocontroller and interface 9 serves as a media access control (MAC)interface between the UWB wireless communication functions implementedby the receiver 11 and transmitter 13 and applications that use the UWBcommunications channel for exchanging data with remote devices.

[0022] The receiver 11 includes an antenna 1 that converts a UWBelectromagnetic waveform into an electrical signal (or optical signal)for subsequent processing. The UWB signal is generated with a sequenceof shape-modulated wavelets, where the occurrence times of theshape-modulated wavelets may also be modulated. For analog modulation,at least one of the shape control parameters is modulated with theanalog signal. More typically, the wavelets take on M possible shapes.Digital information is encoded to use one or a combination of the Mwavelet shapes and occurrence times to communicate information.

[0023] In one embodiment of the present invention, each waveletcommunicates one bit, for example, using two shapes such as bi-phase. Inother embodiments of the present invention, each wavelet may beconfigured to communicate nn bits, where M≧2^(nn). For example, fourshapes may be configured to communicate two bits, such as withquadrature phase or four-level amplitude modulation. In anotherembodiment of the present invention, each wavelet is a “chip” in a codesequence, where the sequence, as a group, communicates one or more bits.The code can be M-ary at the chip level, choosing from M possible shapesfor each chip.

[0024] At the chip, or wavelet level, embodiments of the presentinvention produce UWB waveforms. The UWB waveforms are modulated by avariety of techniques including but not limited to: (i) bi-phasemodulated signals (+1, −1), (ii) multilevel bi-phase signals (+1, −1,+a1, −a1, +a2, −a2, . . . , +aN, −aN), (iii) quadrature phase signals(+1, −1, +j, −j), (iv) multi-phase signals (1, −1, exp (+jπ/N), exp(−jπ/N), exp (+jπ2/N), exp (−jπ2/N), . . . , exp (+j(N−1)/N),exp(−jπ(N−1)/N)), (v) multilevel multi-phase signals (a_(i) exp (j2πβ/N)|a_(i) ε{1, a1, a2, . . . , aK}, βε{0, 1, . . . , N−1}), (vi) frequencymodulated pulses, (vii) pulse position modulation (PPM) signals(possibly same shape pulse transmitted in different candidate timeslots), (viii) M-ary modulated waveforms g_(B) _(i) (t) with B_(i) ε{1,. . . , M}, and (ix) any combination of the above waveforms, such asmulti-phase channel symbols transmitted according to a chirpingsignaling scheme. The present invention, however, is applicable tovariations of the above modulation schemes and other modulation schemes(e.g., as described in Lathi, “Modern Digital and Analog CommunicationsSystems,” Holt, Rinehart and Winston, 1998, the entire contents of whichis incorporated by reference herein), as will be appreciated by thoseskilled in the relevant art(s).

[0025] Some exemplary waveforms and characteristic equations thereofwill now be described. The time modulation component, for example, canbe defined as follows. Let t_(i) be the time spacing between the(i−1)^(th) pulse and the i^(th) pulse. Accordingly, the total time tothe i^(th) pulse is $T_{i} = {\sum\limits_{j = 0}^{i}{t_{j}.}}$

[0026] The signal T_(i) could be encoded for data, part of a spreadingcode or user code, or some combination thereof. For example, the signalT_(i) could be equally spaced, or part of a spreading code, where T_(i)corresponds to the zero-crossings of a chirp, i.e., the sequence ofT_(i)'s, and where $T_{i} = \sqrt{\frac{i - a}{k}}$

[0027] for a predetermined set of a and k. Here, a and k may also bechosen from a finite set based on the user code or encoded data.

[0028] An embodiment of the present invention can be described usingM-ary modulation. Equation 1 below can be used to represent a sequenceof exemplary transmitted or received pulses, where each pulse is a shapemodulated UWB wavelet, g_(B) _(i) is (t−T_(i)). $\begin{matrix}{{x(t)} = {\sum\limits_{i = 0}^{\infty}{g_{B_{i}}\left( {t - T_{i}} \right)}}} & (1)\end{matrix}$

[0029] In the above equation, the subscript i refers to the i^(th) pulsein the sequence of UWB pulses transmitted or received. The waveletfunction g has M possible shapes, and therefore B_(i) represents amapping from the data, to one of the M-ary modulation shapes at thei^(th) pulse in the sequence. The wavelet generator hardware (e.g., theUWB waveform generator 17) has several control lines (e.g., coming fromthe radio controller and interface 9) that govern the shape of thewavelet. Therefore, B_(i) can be thought of as including a lookup-tablefor the M combinations of control signals that produce the M desiredwavelet shapes. The encoder 21 combines the data stream and codes togenerate the M-ary states. Demodulation occurs in the waveformcorrelator 5 and the radio controller and interface 9 to recover to theoriginal data stream. Time position and wavelet shape are combined intothe pulse sequence to convey information, implement user codes, etc.

[0030] In the above case, the signal is comprised of wavelets from i=1to infinity. As i is incremented, a wavelet is produced. Equation 2below can be used to represent a generic wavelet pulse function, whoseshape can be changed from pulse to pulse to convey information orimplement user codes, etc.

g _(B) _(i) (t)=Re(B _(i,1))·ƒ_(B) _(i,2) _(,B) _(i,3) _(, . . .)(t)+Im(B _(i,1))·h _(B) _(i,2) _(,B) _(i,3) _(, . . .) (t)  (2)

[0031] In the above equation, function f defines a basic wavelet shape,and function h is simply the Hilbert transform of the function f. Theparameter B_(i,1) is a complex number allowing the magnitude and phaseof each wavelet pulse to be adjusted, i.e., B_(i,1)=a_(i)∠θ_(i), wherea_(i) is selected from a finite set of amplitudes and θ_(i) is selectedfrom a finite set of phases. The parameters {B_(i,2),B_(i,3), . . . }represent a generic group of parameters that control the wavelet shape.

[0032] An exemplary waveform sequence x(t) can be based on a family ofwavelet pulse shapes f that are derivatives of a Guassian waveform asdefined by Equation 3 below. $\begin{matrix}{{f_{B_{i}}(t)} = {{\Psi \left( {B_{i,2},B_{i,3}} \right)}\left( {\frac{^{B_{i,3}}}{t^{B_{i,3}}}^{- {\lbrack{B_{i,2}t}\rbrack}^{2}}} \right)}} & (3)\end{matrix}$

[0033] In the above equation, the function Ψ( ) normalizes the peakabsolute value of ƒ_(B) _(i) (t) to 1. The parameter B_(i,2) controlsthe pulse duration and center frequency. The parameter B_(i,3) is thenumber of derivatives and controls the bandwidth and center frequency.

[0034] Another exemplary waveform sequence x(t) can be based on a familyof wavelet pulse shapes f that are Gaussian weighted sinusoidalfunctions, as described by Equation 4 below.

ƒ_(B) _(i,2) _(,B) _(i,3) _(,B) _(i,4) =ƒ _(ω,) _(i) _(, k) _(i) _(, b)_(i) (t)=e ^(−[b) ^(_(i)) ^(t]) ² sin (ω _(i) t+k _(i) t ²)  (4)

[0035] In the above equation, b_(i) controls the pulse duration, ω_(i)controls the center frequency, and k_(i) controls a chirp rate. Otherexemplary weighting functions, beside Gaussian, that are also applicableto the present invention include, for example, Rectangular, Hanning,Hamming, Blackman-Harris, Nutall, Taylor, Kaiser, Chebychev, etc.

[0036] Another exemplary waveform sequence x(t) can be based on a familyof wavelet pulse shapes f that are inverse-exponentially weightedsinusoidal functions, as described by Equation 5 below. $\begin{matrix}{{{g_{B_{i}}(t)} = {\left( {\frac{1}{^{\frac{- {({t - {t1}_{i}})}}{3*{tr}_{i}}} + 1} - \frac{1}{^{\frac{- {({t - {t2}_{i}})}}{3*{tf}_{i}}} + 1}} \right) \cdot {\sin \left( {\theta_{i} + {\omega_{i}t} + {k_{i}t^{2}}} \right)}}}{where}\quad \quad {\left\{ {B_{i,2},B_{i,3},B_{i,4},B_{i,5},B_{i,6},B_{i,7},B_{i,8}} \right\} = \left\{ {t_{1_{i}},t_{2_{i}},t_{r_{i}},t_{f_{i}},\theta_{i},\omega_{i},k_{i}} \right\}}} & (5)\end{matrix}$

[0037] In the above equation, the leading edge turn on time iscontrolled by t₁, and the turn-on rate is controlled by t_(r). Thetrailing edge turn-off time is controlled by t₂, and the turn-off rateis controlled by t_(f). Assuming the chirp starts at t=0 and T_(D) isthe pulse duration, the starting phase is controlled by θ, the startingfrequency is controlled by ω, the chirp rate is controlled by k, and thestopping frequency is controlled by ω+kT_(D). An example assignment ofparameter values is ω=1, tr=tf=0.25, t1=tr0.51, and t2=T_(D)−tr/9.

[0038] A feature of the present invention is that the M-ary parameterset used to control the wavelet shape is chosen so as to make a UWBsignal, wherein the center frequency f_(c) and the bandwidth B of thepower spectrum of g(t) satisfies 2f_(c)>B>0.25f_(c). It should be notedthat conventional equations define in-phase and quadrature signals(e.g., often referred to as I and Q) as sine and cosine terms. Animportant observation, however, is that this conventional definition isinadequate for UWB signals. The present invention recognizes that use ofsuch conventional definition may lead to DC offset problems and inferiorperformance.

[0039] Furthermore, such inadequacies get progressively worse as thebandwidth moves away from 0.25f_(c) and toward 2f_(c). A key attributeof the exemplary wavelets (or e.g., those described in co-pending U.S.patent application Ser. No. 09/209,460) is that the parameters arechosen such that neither f nor h in Equation 2 above has a DC component,yet f and h exhibit the required wide relative bandwidth for UWBsystems.

[0040] Similarly, as a result of B>0.25f_(c), it should be noted thatthe matched filter output of the UWB signal is typically only a fewcycles, or even a single cycle. For example, the parameter n in Equation3 above may only take on low values (e.g., such as those described inco-pending U.S. patent application Ser. No. 09/209,460).

[0041] The compressed (i.e., coherent matched filtered) pulse width of aUWB wavelet will now be defined with reference to FIG. 1b. In FIG. 1b,the time domain version of the wavelet thus represents g(t) and theFourier transform (FT) version is represented by G(ω). Accordingly, thematched filter is represented as G*(ω), the complex conjugate, so thatthe output of the matched filter is P(ω)=G(ω)·G*(ω). The output of thematched filter in the time domain is seen by performing an inverseFourier transform (IFT) on P(ω) so as to obtain p(t), the compressed ormatched filtered pulse. The width of the compressed pulse p(t) isdefined by T_(C), which is the time between the points on the envelopeof the compressed pulse E(t) that are 6 dB below the peak thereof, asshown in FIG. 1b. The envelope waveform E(t) may be determined byEquation 6 below. $\begin{matrix}{{E(t)} = \sqrt{\left( {p(t)} \right)^{2} + \left( {p^{H}(t)} \right)^{2}}} & (6)\end{matrix}$

[0042] where p^(H) (t) is the Hilbert transform of p(t).

[0043] Accordingly, the above-noted parameterized waveforms are examplesof UWB wavelet functions that can be controlled to communicateinformation with a large parameter space for making codes with goodresulting autocorrelation and cross-correlation functions. For digitalmodulation, each of the parameters is chosen from a predetermined listaccording to an encoder that receives the digital data to becommunicated. For analog modulation, at least one parameter is changeddynamically according to some function (e.g., proportionally) of theanalog signal that is to be communicated.

[0044] Referring back to FIG. 1a, the electrical signals coupled inthrough the antenna 1 are passed to a radio front end 3. Depending onthe type of waveform, the radio front end 3 processes the electricsignals so that the level of the signal and spectral components of thesignal are suitable for processing in the UWB waveform correlator 5. TheUWB waveform correlator 5 correlates the incoming signal (e.g., asmodified by any spectral shaping, such as a matched filtering, partiallymatched filtering, simply roll-off, etc., accomplished in front end 3)with different candidate signals generated by the receiver 11, so as todetermine when the receiver 11 s synchronized with the received signaland to determine the data that was transmitted.

[0045] The timing generator 7 of the receiver 11 operates under controlof the radio controller and interface 9 to provide a clock signal thatis used in the correlation process performed in the UWB waveformcorrelator 5. Moreover, in the receiver 11, the UWB waveform correlator5 correlates in time a particular pulse sequence produced at thereceiver 11 with the receive pulse sequence that was coupled in throughantenna 1 and modified by front end 3. When the two such sequences arealigned with one another, the UWB waveform correlator 5 provides highsignal to noise ratio (SNR) data to the radio controller and interface 9for subsequent processing. In some circumstances, the output of the UWBwaveform correlator 5 is the data itself. In other circumstances, theUWB waveform correlator 5 simply provides an intermediate correlationresult, which the radio controller and interface 9 uses to determine thedata and determine when the receiver 11 is synchronized with theincoming signal.

[0046] In some embodiments of the present invention, whensynchronization is not achieved (e.g., during a signal acquisition modeof operation), the radio controller and interface 9 provides a controlsignal to the receiver 11 to acquire synchronization. In this way, asliding of a correlation window within the UWB waveform correlator 5 ispossible by adjustment of the phase and frequency of the output of thetiming generator 7 of the receiver 11 via a control signal from theradio controller and interface 9. The control signal causes thecorrelation window to slide until lock is achieved. The radio controllerand interface 9 is a processor-based unit that is implemented eitherwith hard wired logic, such as in one or more application specificintegrated circuits (ASICs) or in one or more programmable processors.

[0047] Once synchronized, the receiver 11 provides data to an input port(“RX Data In”) of the radio controller and interface 9. An externalprocess, via an output port (“RX Data Out”) of the radio controller andinterface 9, may then use this data. The external process may be any oneof a number of processes performed with data that is either received viathe receiver 11 or is to be transmitted via the transmitter 13 to aremote receiver.

[0048] During a transmit mode of operation, the radio controller andinterface 9 receives source data at an input port (“TX Data In”) from anexternal source. The radio controller and interface 9 then applies thedata to an encoder 21 of the transmitter 13 via an output port (“TX DataOut”). In addition, the radio controller and interface 9 providescontrol signals to the transmitter 13 for use in identifying thesignaling sequence of UWB pulses. In some embodiments of the presentinvention, the receiver 11 and the transmitter 13 functions may usejoint resources, such as a common timing generator and/or a commonantenna, for example. The encoder 21 receives user coding informationand data from the radio controller and interface 9 and preprocesses thedata and coding so as to provide a timing input for the UWB waveformgenerator 17, which produces UWB pulses encoded in shape and/or time toconvey the data to a remote location.

[0049] The encoder 21 produces the control signals necessary to generatethe required modulation. For example, the encoder 21 may take a serialbit stream and encode it with a forward error correction (FEC) algorithm(e.g., such as a Reed Solomon code, a Golay code, a Hamming code, aConvolutional code, etc.). The encoder 21 may also interleave the datato guard against burst errors. The encoder 21 may also apply a whiteningfunction to prevent long strings of “ones” or “zeros.” The encoder 21may also apply a user specific spectrum spreading function, such asgenerating a predetermined length chipping code that is sent as a groupto represent a bit (e.g., inverted for a “one” bit and non-inverted fora “zero” bit, etc.). The encoder 21 may divide the serial bit streaminto subsets in order to send multiple bits per wavelet or per chippingcode, and generate a plurality of control signals in order to affect anycombination of the modulation schemes as described above (and/or asdescribed in Lathi).

[0050] The radio controller and interface 9 may provide someidentification, such as user ID, etc., of the source from which the dataon the input port (“TX Data In”) is received. In one embodiment of thepresent invention, this user ID may be inserted in the transmissionsequence, as if it were a header of an information packet. In otherembodiments of the present invention, the user ID itself may be employedto encode the data, such that a receiver receiving the transmissionwould need to postulate or have a priori knowledge of the user ID inorder to make sense of the data. For example, the ID may be used toapply a different amplitude signal (e.g., of amplitude “f”) to a fastmodulation control signal to be discussed with respect to FIG. 2, as away of impressing the encoding onto the signal.

[0051] The output from the encoder 21 is applied to a UWB waveformgenerator 17. The UWB waveform generator 17 produces a UWB pulsesequence of pulse shapes at pulse times according to the command signalsit receives, which may be one of any number of different schemes. Theoutput from the UWB generator 17 is then provided to an antenna 15,which then transmits the UWB energy to a receiver.

[0052] In one UWB modulation scheme, the data may be encoded by usingthe relative spacing of transmission pulses (e.g., PPM, chirp, etc.). Inother UWB modulation schemes, the data may be encoded by exploiting theshape of the pulses as described above (and/or as described in Lathi).It should be noted that the present invention is able to combine timemodulation (e.g., such as pulse position modulation, chirp, etc.) withother modulation schemes that manipulate the shape of the pulses.

[0053] There are numerous advantages to the above capability, such ascommunicating more than one data bit per symbol transmitted from thetransmitter 13, etc. An often even more important quality, however, isthe application of such technique to implement spread-spectrum,multi-user systems, which require multiple spreading codes (e.g., suchas each with spike autocorrelation functions, and jointly with low peakcross-correlation functions, etc.).

[0054] In addition, combining timing, phase, frequency, and amplitudemodulation adds extra degrees of freedom to the spreading codefunctions, allowing greater optimization of the cross-correlation andautocorrelation characteristics. As a result of the improvedautocorrelation and cross-correlation characteristics, the systemaccording to the present invention has improved capability, allowingmany transceiver units to operate in close proximity without sufferingfrom interference from one another.

[0055]FIG. 2 is a block diagram of a transceiver embodiment of thepresent invention in Which the modulation scheme employed is able tomanipulate the shape and time of the UWB pulses. In FIG. 2, whenreceiving energy through the antenna 1, 15 (e.g., corresponding antennas1 and 15 of FIG. 1a) the energy is coupled in to a transmit/receive(T/R) switch 27, which passes the energy to a radio front end 3. Theradio front end 3 filters, extracts noise, and adjusts the amplitude ofthe signal before providing the same to a splitter 29. The splitter 29divides the signal up into one of N different signals and applies the Ndifferent signals to different tracking correlators 31 ₁-31 _(N). Eachof the tracking correlators 31 ₁-31 _(N) receives a clock input signalfrom a respective timing generator 7 ₁-7 _(N) of a timing generatormodule 7, 19, as shown in FIG. 2.

[0056] The timing generators 7 ₁-7 _(N), for example, receive a phaseand frequency adjustment signal, as shown in FIG. 2, but may alsoreceive a fast modulation signal or other control signal(s) as well. Theradio controller and interface 9 provides the control signals, such asphase, frequency and fast modulation signals, etc., to the timinggenerator module 7, 19, for time synchronization and modulation control.The fast modulation control signal may be used to implement, forexample, chirp waveforms, PPM waveforms, such as fast time scale PPMwaveforms, etc.

[0057] The radio controller and interface 9 also provides controlsignals to, for example, the encoder 21, the waveform generator 17, thefilters 23, the amplifier 25, the T/R switch 27, the front end 3, thetracking correlators 31 ₁-31 _(N) (corresponding to the UWB waveformcorrelator 5 of FIG. 1a), etc., for controlling, for example, amplifiergains, signal waveforms, filter passbands and notch functions,alternative demodulation and detecting processes, user codes, spreadingcodes, cover codes, etc.

[0058] During signal acquisition, the radio controller and interface 9adjusts the phase input of, for example, the timing generator 7 ₁, in anattempt for the tracking correlator 31 ₁ to identify and the match thetiming of the signal produced at the receiver with the timing of thearriving signal. When the received signal and the locally generatedsignal coincide in time with one another, the radio controller andinterface 9 senses the high signal strength or high SNR and begins totrack, so that the receiver is synchronized with the received signal.

[0059] Once synchronized, the receiver will operate in a tracking mode,where the timing generator 7 ₁ is adjusted by way of a continuing seriesof phase adjustments to counteract any differences in timing of thetiming generator 7 ₁ and the incoming signal. However, a feature of thepresent invention is that by sensing the mean of the phase adjustmentsover a known period of time, the radio controller and interface 9adjusts the frequency of the timing generator 7 ₁ so that the mean ofthe phase adjustments becomes zero. The frequency is adjusted in thisinstance because it is clear from the pattern of phase adjustments thatthere is a frequency offset between the timing generator 7 ₁ and theclocking of the received signal. Similar operations may be performed ontiming generators 7 ₂-7 _(N), so that each receiver can recover thesignal delayed by different amounts, such as the delays caused bymultipath (i.e., scattering along different paths via reflecting off oflocal objects).

[0060] A feature of the transceiver in FIG. 2 is that it includes aplurality of tracking correlators 31 ₁-31 _(N). By providing a pluralityof tracking correlators, several advantages are obtained. First, it ispossible to achieve synchronization more quickly (i.e., by operatingparallel sets of correlation arms to find strong SNR points overdifferent code-wheel segments). Second, during a receive mode ofoperation, the multiple arms can resolve and lock onto differentmultipath components of a signal. Through coherent addition, the UWBcommunication system uses the energy from the different multipath signalcomponents to reinforce the received signal, thereby improving signal tonoise ratio. Third, by providing a plurality of tracking correlatorarms, it is also possible to use one arm to continuously scan thechannel for a better signal than is being received on other arms.

[0061] In one embodiment of the present invention, if and when thescanning arm finds a multipath term with higher SNR than another armthat is being used to demodulate data, the role of the arms is switched(i.e., the arm with the higher SNR is used to demodulate data, while thearm with the lower SNR begins searching). In this way, thecommunications system dynamically adapts to changing channel conditions.

[0062] The radio controller and interface 9 receives the informationfrom the different tracking correlators 31 ₁-31 _(N) and decodes thedata. The radio controller and interface 9 also provides control signalsfor controlling the front end 3, e.g., such as gain, filter selection,filter adaptation, etc., and adjusting the synchronization and trackingoperations by way of the timing generator module 7, 19.

[0063] In addition, the radio controller and interface 9 serves as aninterface between the communication link feature of the presentinvention and other higher level applications that will use the wirelessUWB communication link for performing other functions. Some of thesefunctions would include, for example, performing range-findingoperations, wireless telephony, file sharing, personal digital assistant(PDA) functions, embedded control functions, location-findingoperations, etc.

[0064] On the transmit portion of the transceiver shown in FIG. 2, atiming generator 7 ₀ also receives phase, frequency and/or fastmodulation adjustment signals for use in encoding a UWB waveform fromthe radio controller and interface 9. Data and user codes (via a controlsignal) are provided to the encoder 21, which in the case of anembodiment of the present invention utilizing time-modulation, passescommand signals (e.g., Δt) to the timing generator 7 ₀ for providing thetime at which to send a pulse. In this way, encoding of the data intothe transmitted waveform may be performed.

[0065] When the shape of the different pulses are modulated according tothe data and/or codes, the encoder 21 produces the command signals as away to select different shapes for generating particular waveforms inthe waveform generator 17. For example, the data may be grouped inmultiple data bits per channel symbol. The waveform generator 17 thenproduces the requested waveform at a particular time as indicated by thetiming generator 7 ₀. The output of the waveform generator is thenfiltered in filter 23 and amplified in amplifier 25 before beingtransmitted via antenna 1, 15 by way of the T/R switch 27.

[0066] In another embodiment of the present invention, the transmitpower is set low enough that the transmitter and receiver are simplyalternately powered down without need for the T/R switch 27. Also, insome embodiments of the present invention, neither the filter 23 nor theamplifier 25 is needed, because the desired power level and spectrum isdirectly useable from the waveform generator 17. In addition, thefilters 23 and the amplifier 25 may be included in the waveformgenerator 17 depending on the implementation of the present invention.

[0067] A feature of the UWB communications system disclosed, is that thetransmitted waveform x(t) can be made to have a nearly continuous powerflow, for example, by using a high chipping rate, where the waveletsg(t) are placed nearly back-to-back. This configuration allows thesystem to operate at low peak voltages, yet produce ample averagetransmit power to operate effectively. As a result, sub-micron geometryCMOS switches, for example, running at one-volt levels, can be used todirectly drive antenna 1, 15, such that the amplifier 25 is notrequired. In this way, the entire radio can be integrated on a singlemonolithic integrated circuit.

[0068] Under certain operating conditions, the system can be operatedwithout the filters 23. If, however, the system is to be operated, forexample, with another radio system, the filters 23 can be used toprovide a notch function to limit interference with other radio systems.In this way, the system can operate simultaneously with other radiosystems, providing advantages over conventional devices that useavalanching type devices connected straight to an antenna, such that itis difficult to include filters therein.

[0069] The UWB transceiver of FIG. 1a or 2 may be used to perform aradio transport function for interfacing with different applications aspart of a stacked protocol architecture. In such a configuration, theUWB transceiver performs signal creation, transmission and receptionfunctions as a communications service to applications that send data tothe transceiver and receive data from the transceiver much like a wiredI/O port. Moreover, the UWB transceiver may be used to provide awireless communications function to any one of a variety of devices thatmay include interconnection to other devices either by way of wiredtechnology or wireless technology. Thus, the UWB transceiver of FIG. 1aor 2 may be used as part of a local area network (LAN) connecting fixedstructures or as part of a wireless personal area network (WPAN)connecting mobile devices, for example. In any such implementation, allor a portion of the present invention may be conveniently implemented ina microprocessor system using conventional general purposemicroprocessors programmed according to the teachings of the presentinvention, as will be apparent to those skilled in the microprocessorsystems art. Appropriate software can be readily prepared by programmersof ordinary skill based on the teachings of the present disclosure, aswill be apparent to those skilled in the software art.

[0070]FIG. 3 illustrates a processor system 301 upon which an embodimentaccording to the present invention may be implemented. The system 301includes a bus 303 or other communication mechanism for communicatinginformation, and a processor 305 coupled with the bus 303 for processingthe information. The processor system 301 also includes a main memory307, such as a random access memory (RAM) or other dynamic storagedevice (e.g., dynamic RAM (DRAM), static RAM (SRAM), synchronous DRAM(SDRAM), flash RAM), coupled to the bus 303 for storing information andinstructions to be executed by the processor 305. In addition, a mainmemory 307 may be used for storing temporary variables or otherintermediate information during execution of instructions to be executedby the processor 305. The system 301 further includes a read only memory(ROM) 309 or other static storage device (e.g., programmable ROM (PROM),erasable PROM (EPROM), and electrically erasable PROM (EEPROM)) coupledto the bus 303 for storing static information and instructions for theprocessor 305. A storage device 311, such as a magnetic disk or opticaldisc, is provided and coupled to the bus 303 for storing information andinstructions.

[0071] The processor system 301 may also include special purpose logicdevices (e.g., application specific integrated circuits (ASICs)) orconfigurable logic devices (e.g, simple programmable logic devices(SPLDs), complex programmable logic devices (CPLDs), or re-programmablefield programmable gate arrays (FPGAs)). Other removable media devices(e.g., a compact disc, a tape, and a removable magneto-optical media) orfixed, high density media drives, may be added to the system 301 usingan appropriate device bus (e.g., a small system interface (SCSI) bus, anenhanced integrated device electronics (IDE) bus, or an ultra-directmemory access (DMA) bus). The system 301 may additionally include acompact disc reader, a compact disc reader-writer unit, or a compactdisc juke box, each of which may be connected to the same device bus oranother device bus.

[0072] The processor system 301 may be coupled via the bus 303 to adisplay 313, such as a cathode ray tube (CRT) or liquid crystal display(LCD) or the like, for displaying information to a system user. Thedisplay 313 may be controlled by a display or graphics card. Theprocessor system 301 includes input devices, such as a keyboard orkeypad 315 and a cursor control 317, for communicating information andcommand selections to the processor 305. The cursor control 317, forexample, is a mouse, a trackball, or cursor direction keys forcommunicating direction information and command selections to theprocessor 305 and for controlling cursor movement on the display 313. Inaddition, a printer may provide printed listings of the data structuresor any other data stored and/or generated by the processor system 301.

[0073] The processor system 301 performs a portion or all of theprocessing steps of the invention in response to the processor 305executing one or more sequences of one or more instructions contained ina memory, such as the main memory 307. Such instructions may be readinto the main memory 307 from another computer-readable medium, such asa storage device 311. One or more processors in a multi-processingarrangement may also be employed to execute the sequences ofinstructions contained in the main memory 307. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions. Thus, embodiments are notlimited to any specific combination of hardware circuitry and software.

[0074] As stated above, the processor system 301 includes at least onecomputer readable medium or memory programmed according to the teachingsof the invention and for containing data structures, tables, records, orother data described herein. Stored on any one or on a combination ofcomputer readable media, the present invention includes software forcontrolling the system 301, for driving a device or devices forimplementing the invention, and for enabling the system 301 to interactwith a human user. Such software may include, but is not limited to,device drivers, operating systems, development tools, and applicationssoftware. Such computer readable media further includes the computerprogram product of the present invention for performing all or a portion(if processing is distributed) of the processing performed inimplementing the invention.

[0075] The computer code devices of the present invention may be anyinterpreted or executable code mechanism, including but not limited toscripts, interpretable programs, dynamic link libraries, Java or otherobject oriented classes, and complete executable programs. Moreover,parts of the processing of the present invention may be distributed forbetter performance, reliability, and/or cost.

[0076] The term “computer readable medium” as used herein refers to anymedium that participates in providing instructions to the processor 305for execution. A computer readable medium may take many forms, includingbut not limited to, non-volatile media, volatile media, and transmissionmedia. Non-volatile media includes, for example, optical, magneticdisks, and magneto-optical disks, such as the storage device 311.Volatile media includes dynamic memory, such as the main memory 307.Transmission media includes coaxial cables, copper wire and fiberoptics, including the wires that comprise the bus 303. Transmissionmedia may also take the form of acoustic or light waves, such as thosegenerated during radio wave and infrared data communications.

[0077] Common forms of computer readable media include, for example,hard disks, floppy disks, tape, magneto-optical disks, PROMs (EPROM,EEPROM, Flash EPROM), DRAM, SRAM, SDRAM, or any other magnetic medium,compact disks (e.g., CD-ROM), or any other optical medium, punch cards,paper tape, or other physical medium with patterns of holes, a carrierwave, carrierless transmissions, or any other medium from which a systemcan read.

[0078] Various forms of computer readable media may be involved inproviding one or more sequences of one or more instructions to theprocessor 305 for execution. For example, the instructions may initiallybe carried on a magnetic disk of a remote computer. The remote computercan load the instructions for implementing all or a portion of thepresent invention remotely into a dynamic memory and send theinstructions over a telephone line using a modem. A modem local tosystem 301 may receive the data on the telephone line and use aninfrared transmitter to convert the data to an infrared signal. Aninfrared detector coupled to the bus 303 can receive the data carried inthe infrared signal and place the data on the bus 303. The bus 303carries the data to the main memory 307, from which the processor 305retrieves and executes the instructions. The instructions received bythe main memory 307 may optionally be stored on a storage device 311either before or after execution by the processor 305.

[0079] The processor system 301 also includes a communication interface319 coupled to the bus 303. The communications interface 319 provides atwo-way UWB data communication coupling to a network link 321 that isconnected to a communications network 323 such as a local network (LAN)or personal area network (PAN)323. For example, the communicationinterface 319 may be a network interface card to attach to any packetswitched UWB-enabled personal area network (PAN)323. As another example,the communication interface 319 may be a UWB accessible asymmetricaldigital subscriber line (ADSL) card, an integrated services digitalnetwork (ISDN) card, or a modem to provide a data communicationconnection to a corresponding type of communications line. Thecommunications interface 319 may also include the hardware to provide atwo-way wireless communications coupling other than a UWB coupling, or ahardwired coupling to the network link 321. Thus, the communicationsinterface 319 may incorporate the UWB transceiver of FIG. 2 as part of auniversal interface that includes hardwired and non-UWB wirelesscommunications coupling to the network link 321.

[0080] The network link 321 typically provides data communicationthrough one or more networks to other data devices. For example, thenetwork link 321 may provide a connection through a LAN to a hostcomputer 325 or to data equipment operated by a service provider, whichprovides data communication services through an IP (Internet Protocol)network 327. Moreover, the network link 321 may provide a connectionthrough a PAN323 to a mobile device 329 such as a personal digitalassistant (PDA) laptop computer, or cellular telephone. The LAN/PANcommunications network 323 and IP network 327 both use electrical,electromagnetic or optical signals that carry digital data streams. Thesignals through the various networks and the signals on the network link321 and through the communication interface 319, which carry the digitaldata to and from the system 301, are exemplary forms of carrier wavestransporting the information. The processor system 301 can transmitnotifications and receive data, including program code, through thenetwork(s), the network link 321 and the communication interface 319.

What is claimed:
 1. A method for conveying digital information withcarrierless ultra wideband wireless signals, comprising: encoding thedigital information into wavelets each having predetermined shapes, theshapes being at least one of bi-phase modulated, quad-phase modulated,multilevel bi-phase modulated, and multilevel quad-phase modulated;transmitting a carrierless ultra wideband waveform via an antenna, theultra wideband waveform including the wavelets; receiving thecarrierless ultra wideband waveform with an antenna; and decoding thedigital information from the wavelets included in the carrierless ultrawideband waveform received in the receiving step.
 2. A method forconveying digital information with carrierless ultra wideband wirelesssignals, as recited in claim 1, wherein the shapes comprise pulsessuitable for a pulse position modulation scheme.
 3. A method forconveying digital information with carrierless ultra wideband wirelesssignals, as recited in claim 1, wherein the digital informationcomprises data bits.
 4. A method for conveying digital information withcarrierless ultra wideband wireless signals, as recited in claim 1,wherein the digital information comprises control data.